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Parked cars stay cooler in shade.

There really is no such thing as a perfect tree. Some are not quite as messy as others. Some have better structural integrity than others. Some have gentle roots; and some stay proportionate to tight spots. However, without exception, all trees grow, drop leaves, and disperse roots.

This is an important consideration when selecting any tree, and especially when selecting a street tree for the narrow space between the curb and the sidewalk (which is commonly known as a park strip). Even where there is no sidewalk, or where the sidewalk is at the curb, most of the obstacles are the same.

Street trees should have reasonably complaisant roots that should not be likely to damage curbs, sidewalks or roadways, at least for several years. They should naturally develop reasonably high branches. They will need to be pruned higher than trucks that may park at the curb. Street trees must also tolerate harsh exposure.

Wider park strips can of course accommodate larger trees. Those that are only two feet wide or narrower are probably not wide enough for any tree larger than photinia, purple-leaf plum or English hawthorn, which are difficult to prune for clearance over roadways and sidewalks.

Messy leaves, flowers or fruit that might not be a problem within the garden might be more of a problem at the curb. It is not so easy to rake such debris if cars park over it. Trees that are commonly infested with scale or aphid are likely to drop sticky honeydew (scale and aphid poop) onto parked cars.

Unfortunately, those who get street trees do not always get to select them. Many municipalities assign specific trees to specific streets. Some streets have a few trees to choose from. Others have only one option. Home Owners’ Associations (HOAs) decide if and where new trees get planted.

Crape myrtle is probably the most common choice for a new street tree because the roots do not get big enough to damage pavement. However, the canopies are not very big either. They stay too low to be pruned above trucks. Crape myrtle is susceptible to scale infestation that can get bad enough to make sidewalks sticky.

For many years, London plane (sycamore) had been another popular street tree. Unfortunately, the voracious roots can damage pavement within only a few years. The messy foliage discolors and starts to fall before autumn.

4 thoughts on “Streets Are Cooler With Shade

  1. I even had sycamore growing in my garden from the flying seeds they develop. I noticed it is advisable to remove them immediately as they can begin to take over useful space, although they did attract a few interesting insects.

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    1. It is certainly not a good choice for confined spaces. We plant many as street trees in Los Angles, but only where there is plenty of space between the curb and sidewalk for the wide trunk. Fortunately, the roots of the native sycamore are quite complaisant. Since they are native, they are resilient to the climate. Other sycamores work well too, but prefer to be in landscaped areas where they get a bit of water through summer. They all got anthracnose rather badly this year, so are just now making a new batch of foliage. There are many where I work, and some grand specimens in the forest.

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  2. I’ve noticed the ornamental cherry trees seeming a great choice as a street tree around town this year. They are a good size too. I imagine they were planted at much the same time, so if they have a set lifespan, that might be different. I love to see ginkgos but I have never seen one used as a street tree so far as I can remember – only ever in gardens.

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    1. Both are excellent choices in most municipalities. However, the flowering cherries do not work so well here because they are so susceptible to sun scald. In other parts of the landscapes, lower growth can be left long enough for upper canopies to disperse and shade the trunk below. As street trees, we must remove the lower growth and prune the trees up high early on, leaving the trunks too exposed. Those that were planted as street trees in Nihonmachi (Japantown) in San Jose are doing nicely so far. People just needed to walk around them and avoid hitting them with high profile vehicles for the first few years. They live only about half a century here, but that is just fine for most of us. Ginkgo is an exceptional street tree. It eventually gets quite tall, but is remarkably complaisant. The main problem is that it grows rather slowly, so does not do much for a street until it is several years old. Old trees made objectionable fruit, but modern trees are fruitless male clones.

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